Polarization-independent frequency-selective rasorber with a broadened absorption band

Abstract

A polarization-independent frequency selective rasorber (FSR) with a transmission band at high frequency and a broadened absorption band at low frequency is designed and analyzed in this paper. The FSR consists of a resistive sheet and a bandpass frequency selective surface (FSS). A strip-type micro resonator (MR) is developed and applied in the resistive element. The MR is equivalent to a parallel LC circuit and resonates at the transmission band. The induced surface current distributions on the resistive element at different frequencies can be controlled as expected using the MRs, so that a high in-band transmission at high frequency and an absorption band at low frequency can be obtained, which are almost independent to each other. The absorption bandwidth can be broadened by cascading more MRs with several resistor-loaded metallic strips. Besides, due to the tiny dimensions of the MRs, polarization-independent absorptive/transmissive performances can be achieved by printing two orthogonal arrays of resistive elements on different surfaces of a dielectric substrate. The performance of the FSR is verified by both numerical simulation and experimental measurement.